. ipc wants to know about processes that get
signals, so that it can break blocking ipc operations
. doing it for every single signal is wasteful
and causes the annoying 'no slot for signals' message
. this fix tells vm on a per-process basis it (ipc)
wants to be notified, i.e. only when it does any ipc calls
. move ipc config to separate config file while we're at it
Headers that will be shared between old includes and NetBSD-like includes
are moved into common/include tree. They are still copied in /usr/include
in 'make includes', so compilation and programs aren't be affected.